Alloys



Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE ALLOYS No Drawing.Application March 21, 1936, Serial No. 70,112

4 Claims.

My invention relates to alloys which are adapted as substitutes for thewell known gold-palladium alloys, now used for the manufacture of pins,

washers and other auxiliary elements in the den- 5 tal industry.

The object of the invention is to provide a new alloy composed of theprecious metals palladium, platinum and gold, the palladium preferablybeing present in greater proportion than the platinum, and the gold inlesser proportion than the platinum.

An alloy containing substantially 60% palladium, 30% of platinum and 10%of gold has been found particularly satisfactory.

The well-known gold-palladium alloys are used as a substitute for gold.Palladium is added to the gold regularly in amounts from 30 to 40%; theresulting alloys melt around 1400" C.

When these gold-palladium alloys are shaped into thin wires, ribbons andthe like, they behave, mechanically, much the same as pure palladium inthat the alloys smear and are very hard on the rolls and dies,necessitating the cleaning of the rolls and dies within short workingperiods. When these alloys are shaped into dental pins or washers on thewell known automatic machines they are always obtained with rough edges,because these alloys drag considerably from the tools and the minutepunches and dies used in the machines have to be changed and cleanedevery few hours.

Although these gold palladium alloys are harder than pure palladium theypreserve all of the mechanical properties so characteristic of the pure3? palladium metals even when alloyed with about 60 to 70 parts of gold.The addition of small amounts of rhodium or iridium does not favorablychange the property of these alloys, but on the other hand increases thehardness of these alloys 40 with the result that the mechanicaldifilculties are accordingly increased.

It has been found that all these purely mechanical difficulties can beovercome and these alloys can be improved in many other directions 45when the regularly predominating gold content of these alloys is greatlyreduced, and when platinum is added in such proportion that palladiumand platinum together become the main constituents of the alloys.Special tests have shown that the most favorable change in themechanical properties of the gold-palladium alloys takes place as soonas the gold content is reduced to less than 25%, and when these alloyscontain at 55 least 15% platinum. In other words, the most favorableresults are obtained with alloys comprising as constituents:

The ternary alloys resulting from these combinations, especially thosewith gold contents not higher than 5 to 15% are extremely easy to work.10 They show nearly the same mechanical properties as platinum (highductility) and when shaped into wires, sheets, ribbons, pins, etc. theyhave the same color and high brillliancy as platinum, but never thedullness which is so char- 15 acteristic of the gold-palladium orpalladiumgold alloys. My new alloys melt nearly all around 1500 C.; theyare, therefore, especially adapted to be used as auxiliary metalelements in the manufactrue of artificial teeth, especially, since theypreserve a very high tensile strength up to 1400 0., and, as tests haveshown, adhere excellently to the porcelain, when baked together with theporcelain used for the manufacture of artificial teeth.

These ternary alloys may contain also some of 25 the other metals of theplatinum group, such as rhodium, iridium, ruthenium and osmium, singlyor collectively in minor amounts, (about 0.5-2%; these platinum groupby-metals are often present in these amounts in the commercial grades ofplatinum and palladium). These minute amounts (5% to 2%) of the metalsof the platinum group will increase the tensile strength of theseternary alloys to ahigh degree as well as the corrosion resistancethereof without changing the good mechanical properties mentioned above.

I have found that the, presence of rhodium and/or iridium is especiallyadvantageous; these by-metals of the platinum group practicallyvolatilize in these alloys only in a very minor degree when the alloysare used at temperatures above 1100 C. Similarly, the mechanicalproperties of these alloys are not essentially changed when smallamounts of the metals of the iron group 5 (iron, cobalt, nickel) arepresent in these alloys alone or together with minor amounts of themetals of the platinum group (rhodium, iridium, ruthenium, osmium).These metals of the iron group can be present, singly or incombinations, in amounts up to approximately 3%. The metals of theplatinum group, as well as the metals of the iron group, do not changethe general character of these alloys, since all of these metals, whenthey are added singly or in combination in to and up to a platinumcontent of about- The other combinations are best worked in the coldstate, withintermediate annealings, and

by quenching them in water after such annealings.

asrinc, cadmium, tin, manganese, rhenium, chromum, etc. can be presentin these alloys in minor amounts up to 3% without impairing the originalproperties of these alloys. The presence of the metals with low meltingpoints, (such as zinc, cadmium, tin, silver, copper) in such minoramounts does not even change substantially the melting points and thecorrosion resistance of these alloys. The tensile strength of thesealloys is, however, increased and in a similar way as with the additionof the metals of the platinum group (rhodium, iridium, osmium,ruthenium) or those of the iron group. These alloys are best worked inthe cold state and with intermediate annealings and by quenching them inwater after such annealing.

In case these alloys shall be used for dental casts of small dimensionsand these casts are not to be worked mechanically afterwards, but justfashioned to the purpose intended, there can be produced with thesealloys excellent com binations in which the meltingpoint of the liquidalloys isdecreased; the liquidity is increased by adding to the melts offrom 1 to 4% of phosphorous. Since these alloys absorb rather largeamounts of oxygen when in the liquid state, the phosphorous practicallyto be added has to be in excess of this amount, since part: of it actsas a dioxidizer.

The alloys of the specified system do not show an essential improvementwhen submitted to the well-known heat-treatment processes; they rep-'resent systems in which the constituents are in complete solid solution.

The palladium-platinum alloys, with the constituents specified above,are of great technical value because they have a high melting point,high tensile strength up to highest temperatures used in the dentalindustry, and because they possess the brilliancy and color of platinumand all the other excellent mechanical properties outlined above. Theyare besides very highly corrosion resistant. Palladium is very readilysoluble in boiling nitric acid *and also are most of the palladiumalloys with a high palladium content. The new alloysresist boilingconcentrated as well as diluted nitric acid and also boilingconcentrated hydrochloric acid. These alloys are,

therefore, not only of great use in the dental industry but they canalso be used with great advantage, for the manufacture of pens forfountain pens, instead of gold alloys, and in the chem- -ical industry.Last but not least, these new alloys offer a great economical advantage.As long as the price of gold is higher than the price of platinum orequal thereto, these alloys are milch cheaper than the regularly usedgold alloys with gold as a predominant constituent. Likewise are alwaysof special advantage the alloys with 50% palladium and more; especiallysince all the alloys with such high palladium content do. not exceed intheir specific gravities the value of Even silver and copper, and alsosuch metals Tensilityzhard reduced) 15 essentially, which specificgravity is far below the values attained with alloys containing gold andplatinum as predominating constituents.

Examp es (1) The alloy consisting of 60% palladium, 30% platinum, 10%gold has the following properties: 7

Melting point: 1506 C. Specific gravity: 15.25. Tensility: hard (75%reduced) 74 kilograms per square'millimeter. soft (annealed 1 hour at1400 C.)

27.3 kilograms per square millimeter.

2)."rhe alloy consisting of 59% palladium, 30% platinum, 10% gold, and1% rhodium has the following properties:

Melting point: 1515 c.

" Specific gravity: 15.20.

Tensility: hard (75% reduced) 79 kg./per square millimeter. soft(annealed 1, hour at 1400 C.)

27.6 kilograms per square millimeter. Corrosion: Loss per squarecentimeter-one hour Boiling conc. HCl .14 milligram.

Boiling conc. I-INO: .021 milligram.

(3) The alloy consisting of 58% palladium,

30% platinum, 10% gold, 1% rhodium, and l%' iridium has the followingproperties:

Melting point: 1538 C. Specific gravity: 15.30.

Tensility: hard (75% reduced) 78.3 kilograms per square millimeter. soft(annealed 1 hour at 1400 C.)

34.4 kilograms per square millimeter.

Corrosion: Loss per square centimeter-one hour Boiling conc. H01 .008milligram.

Boiling conc. HNOa. .012 milligram.

(4) The alloy consisting of 58% palladium, 30% platinum, 10% gold and 2%silver has the following properties: 1 e,

Melting point: 1498 C. Specific gravity: 15.08.

'Tensility: hard (75% reduced) 94.4 kilograms per square millimeter. Isoft (annealed 1 hour. at 1400 .C.)

28.2 kilograms per square millimeter.

Corrosion: Loss per square centimeter-one hour Boiling conc. H01 .008milligram. Boiling conc. HNO: .011 milligram.

(5) The alloy. consisting of 60% palladium,

27% platinum, 10% gold, 3% nickel has the following properties:

Melting point 1463 C. Y Specific gravity: 14.68.

105.3 kilograms per square millimeter.

' soft (annealed 1 hour atl400 0.5

35.7 kilograms per square millimeter. Rockwell hardness ball, 100 kg.)

' soft 73.8.

reannealed 75.2. Corrosion: Loss per square centimeter-one hour Boilingconc. H01 .020 1' 1 Boiling conc. H: .029

(6) The alloy consisting of palladium, 27% platinum, 10% gold, 3% zinc,has the following properties:

Rockwell hardness (fiy'ball, kg.)

soft 70.8. reannealed 78.0. Corrosion: Loss per square centimeter--onehour.

Boiling conc. H01 .041 milligram.

Boiling conc. I-INOs .084 milligram.

As the examples show, the new alloys include mostly alloys with amelting point nearly as high as that of pure palladium (1555 C.).Compared with pure palladium these new alloys are, however, much morecorrosion resistant than palladium. Palladium is, like silver, veryreadily soluble in diluted nitric acid. The alloys have not the dullnessof palladium but the brilliancy of platinum and also all the other goodmechanical properties of platinum, but combined with a greater naturalhardness and a greater tensile strength than platinum or palladium. Theytherefore, excel in every manner palladium and also the much usedgold-palladium alloys.

In'the appended claims where the expressions commercial platinum andcommercial palladium" and commercial gold are used, it is understoodthat these terms refer to platinum and palladium and gold as thesemetalsare available on the open market for every day commercial use orwhen taken from the various stages of the refining processes. Commercialpalladium and commercial platinum, as is well known to persons skilledin the art, may contain up to 2% other metals of the platinum group(iridium, rhodium, osmium, ruthenium), minor amounts of the metals ofthe iron group (which are, to a certain degree related to the metals ofthe platinum group); minor amounts of silver and copper (which aresimilar to gold) and also minor amounts of such substances as zinc,cadmium or tin may be present in various grades of the commercially usedgold. The presence of such elements (altogether not more than up to 6%)does not materially change thecharacter of the described and specifiedpalladium/platinum/gold alloys; but they do, when present, improveslightly these alloys as to their natural hardness.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. An alloy consisting of 60% of palladium, 30% of platinum and 10% ofgold.

2. A dental element in the form of a shaped member coinformableto adental condition, said member being made from an alloy consisting of 60percent of palladium, 30 per cent of platinum, and 10 per cent of gold.

3. An alloy consisting of 15 to 50% platinum 5 to 20% gold, the remainerof the alloy being palladium.

4. A dental element in the form of a shaped member conformable to adental condition, said shaped member being made from an alloy consistingof 15 to 50% platinum, 5 to 20% gold, the remainder of the alloy beingpallidium.

J OHANN SIMON S' I'REICH ER.

